NVIDIA GPU example with working CUDA

issue #1547

Previosly two commands are run; the first enables it for every start; the second start's it.
systemctl has a option at `enable` and `disable` that allows to start or stop it directly without a second command

```bash
$ systemctl --help | grep now                                              
     --now               Start or stop unit after enabling or disabling it
```

issue #1507